As far as I know, the only way to check the PCM is to replace it, if it hasn't thrown any codes, but it's pretty unlikely that this is the problem if it hasn't. If you're not getting any codes, and if it's running well once it starts, then it probably isn't the PCM.
Can you give some details on what the starting problem is?
Note, I might be slow in responding. I'm visiting relatives, hijacking my brother-in-law's computer, and may not get as many chances to log on as usual.